A 1st Class Soldier in the making with a simple yet passionate dream of becoming a hero. Enthusiastic, passionate and positive. He will take on any mission to prove his worth to the Shinra company. Also popular among the women in Midgar, he soon gets his own fan club.

Zack left his home town of Gongaga at the age of fourteen to join the Shinra Electric Power Company's military forces. He was promoted to Soldier 2nd Class sometime in the next two years.

Unlike many Soldier members, he has a 1st Class mentor named Angeal Hewley.

During the war against Wutai, Angeal vanished and later returned as Zack's enemy. Zack was then promoted to Soldier 1st Class at the age of sixteen. However, he could not feel happiness at the time, as he and Sephiroth were ordered to pursue former friends Angeal, and Genesis. After a twist of events, Angeal told Zack to fight him to protect his honor; to kill him, right before he had completely turned into a monster via "Project G." After their battle, Angeal regains his sanity and hands the Buster sword down to Zack in his dying moments. He encourages Zack to carry on both their dreams and honor. Zack's signature X-shaped scar on his cheek was given to him by Angeal in their battle.

Sometime during his Soldier 2nd class days, Zack meets a girl named Aerith in the Church in the Slums. Their feelings begin to blossom over time and they become potential love interests. Aerith especially stayed by Zack's side as he mourned Angeal's death during the two years before he was actively working again. Although duty and antagonists get in the way of their relationship, Zack and Aerith often kept in contact. Even after Zack went missing for four years in Nibelheim, Aerith continued to write him letters. She sent a total of 89 letters within that time before she had finally given up. The ribbon that Aerith is always seen wearing in her hair was gifted by Zack during a date. It was also their mutual idea to start selling flowers in Midgar.

Zack dies at the age of 23 while protecting a "mako poisoned" Cloud Strife from the Shinra Corporation, after escaping Nibelheim. The two were test subjects for four years after the Sephiroth incident, and were to be treated as "killed in action." Zack's final stand was against the entirety of Shinra's infantrymen, and he defeats all but three before finally exhausting his stamina. Left on the plains to die, in his final moments, he hands down the Buster Sword to the half-conscious Cloud, just as Angeal had done with him. He encourages him to be his "Living Legacy" and to live for the both of them; to carry on his dreams and honor. Parting the world with a smile, his final words were "say hi to Aerith for me," and "hey, would you say I became a hero?"